The Bartimaeus series is set in an alternate-history world, in which the British Empire is ruled by a council of magicians who bind demons/spirits to their will and subjugate non-magical "commoners". This magical empire was founded by William Gladstone, a powerful magician who overthrew the previously dominant Czech empire based in Prague. The series is set in the early 21st century, with approximately 1950s-level technology (plus magic), but the British Empire still appears to be fighting in the American War of Independence. Wikipedia claims that the Roman empire survived until the 19th century and was then replaced by the Czech empire, but this claim has no citation and appears to be incorrect.
How much of the alternate history timeline can we piece together? We have a big advantage in the viewpoint character of Bartimaeus, who's been enslaved to human magicians for thousands of years and often brings up anecdotes from his past, sometimes even discussing the rise and fall of empires on a global level. How much can be pieced together from his remarks across the three books1 about the history of the world in this story?
1 (Got to do a footnote, in true Bartimaeus style.) Taking into account the fourth prequel book, The Ring of Solomon, is OK, but please list separately any conclusions drawn from there, as I'm not really sure how consistent it is with the history of the main trilogy - especially given the way Bartimaeus refers to Solomon in the latter.